Negative Density for POP Prints?

Discussion in 'Alternative Processes' started by mmcclellan, Apr 17, 2005.

  1. mmcclellan

    mmcclellan Subscriber

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    Quick question -- should negative densities for POP prints be the same as for platinum/palladium prints? I am about to start doing those and understand (correct me if I'm wrong!) that neg densities for p/p should be about two stops over and the neg be overdeveloped by about 100%. Is this true? And if so, should negs for POP prints be equally dense and contrasty?

    Any guidance on this will be much appreciated. From what I'm reading, it seems that negs for most or all of the alternative processes should be similarly over-exposed and over-developed.

    Thanks, everyone!
     
  2. Ole

    Ole Moderator Staff Member Moderator

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    Contrast range (not density) for POP should be as high as possible or thereabouts. I have found it very difficult to achieve sufficient contrast in modern materials without staining developers. A CI of 1.8 to 2.4 has been said to be optimal, but I don't own a densitometer so I can't tell.
     
  3. noseoil

    noseoil Member

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    Take a look at the density range of Efke 25 at J&C's web site at the bottom of the front page ( http://www.jandcphotography.com - Efke Technical data link). I think you will find it builds contrast readily, in a relatively straight line, from .7 at the top of the toe to about 3.0 at the shoulder. This should be sufficient for most needs, and some we haven't even dreamed up yet.

    Efke 100 will do a good job as well, not as picky about development times and exposure, but it builds density quite well also. Add a staining developer (like Pyrocat or PMK pyro) and you have a winner with good highlight separation and a long straight line. tim

    P.S. Ole, if you haven't played with these films, please give it a try some time. With your experience in films it would be fun to see how you can manipulate it to suit your needs. Really great stuff, but a bit slow on the shutter. The nice thing about it is to be able to kick it up off the toe and still have plenty of development left for highlights.
     
    Last edited by a moderator: Apr 17, 2005
  4. smieglitz

    smieglitz Subscriber

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    You'll need more density and contrast for POP than you will for Pt/Pd or almost any other alternative process exclusing salted paper and albumen printing which are closely related.

    IME negatives don't need to be overexposed by a full two stops to work well but some additional exposure should be given. More development is definitely called for in order to raise the contrast and highlight densities.

    Joe
     
  5. smieglitz

    smieglitz Subscriber

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    Ole,

    You do need to really boost the development contrast quite a bit, but I've never heard of a pictorial film being able to achieve those CI figures. (Perhaps some technical or graphic arts films could.) Do you mean the density range, DR of the negative should be 1.8 to 2.4,? If not, could you please indicate where you found those CI recommendations?

    I would suspect that a CI of about .85 or thereabouts would produce a negative contrast suitable for POP. (Just a guess based on my experience with POP. I too lack a reflection densitometer and have never measured one of my POP negatives with a transmission densitometer, but I doubt any negative I've made for any alternative process exceeds a CI of 1.0. You've sparked my curiosity so now I'll have to pull one out and actually measure the CI and DR.) Normal CI figures for negatives intended for regular enlarging papers would be in the .44 to .60 CI range.

    There are also some problems with how density range figures are derived and quoted by various authors so someone is probably better off running a few quick tests with a stepwedge to determine the exposure scale of the paper and then developing their film to the appropriate contrast.

    Joe
     
  6. Ole

    Ole Moderator Staff Member Moderator

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    Of course I've played with them! First time I used EFKE R25 and R50 they were called R14 and R17, back before the ISO standard - around 1978?

    I have a few hundred sheets of 4x5" EFKE PL25 in the freezer, which I bought just before I more or less switched to 5x7" and 9x12cm.

    So far I have used Ilford FP4+ and MACO UP100+ for POP - the MACO needed a bleach-and-redevelop with pyro/NaOH to get enough highlight contrast. FP4+ can work straight from a non-staining developer, but staining is better. The Pextral 2-bath in the chemical formulas gave great results with FP4+ and a low-contrast subject.
     
  7. mmcclellan

    mmcclellan Subscriber

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    Great information, friends! Thanks! It seems the consensus is that the density and contrast have to be even higher than for most other alternative processes. At least now I know the direction in which I need to experiment. Thanks again.
     
  8. smieglitz

    smieglitz Subscriber

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    I pulled out an 8x10 negative that prints very well on Centennial POP and as near as I can tell it has a Contrast Index (CI) of about 1.06 and density range of approximately 1.96 measured from Zone II to Zone VIII.

    Also, Sandy King's article on unblinkingeye.com gives similar CI target values of around 0.90 to 1.0 for albumen and salted paper, and POP would be right up their with those sister processes. See:

    http://unblinkingeye.com/Articles/PCat/PCat4/pcat4.html


    Joe
     
    Last edited by a moderator: Apr 18, 2005
  9. Kerik

    Kerik Member

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    This hasn't been my experience. I've done alot of POP printing and most of my pt/pd negs that I've also printed in POP have worked very well. I don't have or use a denistometer, so I can't give you numbers. I primarily shoot FP4+, Forte and HP5+ developed in PMK or Rollo Pyro. It's been my experience that POP is quite flexible and can handle a range of different negs. FYI, I've used POP with both a UV tube box and a NuArc plate burner. I get a little more contrast with the UV box.

    Kerik
    www.kerik.com
     
  10. mark

    mark Member

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    I asked Bostic and Sullivan almost this same question. Here is what they told me-Yes, the negative needs to be dense and contrasty. How you describe the neg for Pt/Pd is also the way they described it to me, as a starting point if one does not have a densitometer, and no plans to get one. From that point, according to them with trial and error plus good notes one will get there eventually.

    The method has thus far worked for me. I am starting to get negs that print well on POP
     
  11. smieglitz

    smieglitz Subscriber

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    Could well be. I have no experience with Pt/Pd so I'm only relating what I've read from various sources in regard to those processes.

    I know that in my experience, negatives for van dyke brown and POP, salted paper and albumen require negatives of greater density range and contrast than cyanotypes and the reported optimal density ranges for cyanotype and Pt are less and closer to each other than they are to VDB, POP, albumen and salted paper.

    Joe
     
  12. Ole

    Ole Moderator Staff Member Moderator

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    I meant density range. not CI. These recent terminology fights have made even more confused, it seems:wink:

    In my limited experience salted paper needs most contrast, followed by (decreasing order) POP, albumen, VDB, AZO(?), cyanotype. Cyanotype and "ordinary" enlarging paper are about the same, depending on light source for the cyano and grade/developer for the enlarging paper.